1) Field of the Invention
The present invention relates to a monitoring system and a monitoring method capable of monitoring a person's movements while maintaining privacy.
2) Description of the Related Art
FIG. 7 is a block diagram that shows the components of a conventional behavior monitoring device and a behavior monitoring and supporting system disclosed in Japanese Patent Application Laid-Open No. 2000-000216. The disclosed system has a behavior monitoring device 102A and a monitoring device 103. The behavior monitoring device 102A includes a video camera 107 set in a living area 105 that monitors a person 106, and an image processing computer 108A that processes a signal obtained in the video camera 107. The monitoring device 103 monitors an image signal transmitted from the behavior monitoring device 102A in a remote place. The monitoring device 103 is connected to the behavior monitoring device 102A through the internet. The video camera 107 continuously picks-up an image of the person 106.
The image signal picked up by the video camera 107 is converted into a digital image signal by an image converter 109 in the image processing computer 108A. The image converter 109 executes a predetermined correction with respect to the signal and supplies it to an abstraction processor 110. The abstract processor 110 makes the image of the person abstract, based on an abstracting process, to protect the privacy of the person. The abstracting process is, for example, applying mosaic to a part of the image (first method). On the other hand, a difference between the real image and a background image, i.e., an image of the person alone is obtained, and the difference image is blacked out (second method). The abstract image signal is supplied to an image compressor 111 that compresses the signal. The compressed image signal is stored along with the time information in an image storage 112.
When the monitoring device 103 makes an access to the image processing computer 108A, an image extractor 113 extracts the stored time-series image signals and transmits them to the monitoring device 103 through a transmitter 114 and the Internet. A receiver 115 in the monitoring device 103 receives the image signals through the Internet. An image reproducer 116 reproduces the image signals. A display 118 displays the image signals. Thus, an abstract image of the person 106 is displayed on the display 117.
When the first method is employed as the abstracting process, there arises a problem that the person's movements cannot be read in detail. When the second method is employed as the abstracting process, there is a problem that a pick-up range of the video camera 107 becomes limited. In addition, if there is considerable movement in the image pick-up area, images picked-up for a considerable period are required to be averaged to obtain the background image, and sometimes the background image can not be obtained at all.